A new U.S. study suggests drinking three or more cups of caffeinated coffee a day increases the risk of vision loss or blindness.

On the other hand, researchers found regular pop, tea, chocolate or decaffeinated coffee didn't have an impact on sight.

The study looked at two American cohorts, nearly 79,000 women and more than 41,000 men, all over the age of 40. They answered questionnaires about how much java they drink, and researchers looked at their medical records for exfoliation glaucoma — which causes increased eye pressure that could damage the optic nerve and lead to vision loss.

Heavy caffeinated coffee drinkers were found to be at greater risk of developing exfoliation glaucoma than those who don't drink coffee. Researchers found women with a history of the condition have an increased risk.

Dr. Jae Hee Kang, the study's author based at the Brigham and Women's Hospital in Boston, Mass., said Scandinavian residents have the highest rates of glaucoma in the world and also drink the most caffeinated coffee. In a previous study, they linked heavy coffee intake with an increased risk of primary open-angle glaucoma.

Kang said further study in more places around the world is needed.

"Because this is the first study to evaluate the association between caffeinated coffee and exfoliation glaucoma in a U.S. population, confirmation of these results in other populations would be needed to lend more credence to the possibility that caffeinated coffee might be a modifiable risk factor for glaucoma," Kang said.

The study was published Thursday in the Investigative Ophthalmology & Visual Science journal.

As with all stories of this type, it's important to actually read the study rather than read what a journalist wrote based on the press release written on what the journal or university press officer understood from the researchers. The DOI of the study is 10.1167/iovs.12-10085. Understanding what the risks mean is also important.

Firstly, the observations only show any statistical significance in women, as there weren't enough men in the study that showed cases of glaucoma. Secondly, the relative risk is about 1.4 - 1.6 in the highest (>3 cups, or >500mg caffeine per day ) consumption groups, for a 50% increase in risk. Thirdly, the relative risk is starting from a small base, 360 cases total out of 120,000 plus participants. So a 1 in 300 chance among the participants of getting glaucoma is increased to 1 in 200 for very high coffee consumption group. A positive family history of glaucoma or obesity are much bigger factors in altering the risk. This is before you take into consideration any systematic effects in the study to do with the characteristics of the cohort studied (all members were nurses or health professionals).

I recall hearing about a similiar study over 20 YEARS AGO about drinking coffee too fast causing increased blood pressure leading to increased intraocular pressure leading to glaucoma. Yet here I am, almost 50 and still no glasses.

Len

"Coffee leads men to trifle away their time, scald their chops, and spend their money, all for a little base, black, thick, nasty, bitter, stinking nauseous puddle water." ~The Women's Petition Against Coffee, 1674

Hold on a second, the subject line was: "Heavy coffee drinkers at increased risk of blindess: Study"

So shouldn't your comment be: "And milk in coffee? - murderous obese people bludgeoning people to death with their white canes ..."

Ouch.

Len

"Coffee leads men to trifle away their time, scald their chops, and spend their money, all for a little base, black, thick, nasty, bitter, stinking nauseous puddle water." ~The Women's Petition Against Coffee, 1674

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